1. Field of the Invention
The present invention relates to a device allowing one to introduce a product, particularly a pulverulent product, from a chamber A having a pressure P1, into a chamber B having a pressure P2 higher than P1.
According to one of the most widely known techniques, devices of this type are designed to introduce a pulverulent product -- which is at ambient pressure -- into a conduit under pressure, which provides for the pneumatic conveyance thereof; for this purpose, a gaseous flow runs through the conduit at such a pressure and speed that it is capable of carrying along the solid product to be conveyed, from a starting point X towards an arrival point Y. For this purpose, a pump keeps between the points X and Y a pressure difference equal to the pressure losses produced by the circulation, at the intended speed, of a mixture of the gas and the product being conveyed.
Gaseous flow pumps do not however allow the passage of solid materials, other than in minimum proportions in respect of the volume of the pumped fluid. Consequently, one is inclined to place said pump, either upstream of the point of introduction of the product, or downstream of the collection point of the product, that is, either before the poing X, or after the point Y.
It is hence necessary to use a device allowing one to introduce the product into the conduit under pressure between the points X and Y, said device being generally called an introducer: such introducers are at present known and on the market, in various types of constructions.
2. Description of the Prior Art
A first known construction consists of passage tanks, which are alternatively brought to room pressure, to be filled with material, and subsequently to the pressure of the conduit to allow the passage of the material towards the latter. However, these tanks have necessarily the drawback of being scarcely safe, due to their complex structure, besides being very costly and notably bulky.
A further construction consists of rotary gates, having the advantage that they work continuously: they are extremely simple and safe, but they do not allow one to exceed pressure differences higher than 600 millibars. They have no abrasion resistance and they usually have considerable gas leaks.
A still further construction of introducers of solid substances into a gaseous flow, consists of a worm screw device having non-constant pitch. Such device, which is highly simple and safe, has the drawback of using too much energy, of being limited to a pressure difference of about 2 bars, of having a poor resistance to abrasion, and finally, of being unemployable for fragile or thermosensitive products, the compression and temperature increase of the product in the last turn of the screw being actually considerable.
There are also continuous pneumatic elevators, consisting of a tank inside which the product to be conveyed is fluidified over a height equal to the back-pressure which should be obtained. Elevators of this type are particularly interesting for the numerous practical advantages which they provide, in particular: great safety in working, low energy consumption with low power, very good abrasion resistance, and continuous working. However, the drawback of such a device lies in the remarkable height which is normally required for the tank in which the product is fluidified: in fact, with a product having a specific gravity of about 1, it is necessary to use a tank having a height of about 10 m. in order to obtain a pressure difference of 1 bar.